Overview

Photophobia (also light sensitivity) or fear of light, is a symptom of excessive sensitivity to light and the aversion to sunlight or well-lit places. In medical terms, it is not fear, but an experience of discomfort or pain to the eyes due to light exposure.

Pathophysiology

Light sensitivity is usually due to too much light entering the eye, which causes over stimulation of the photoreceptors in the retina and subsequent excessive electric impulses to the optic nerve. This leads to a reflex aversion to light, and discomfort or pain.
Too much light can enter the eye if it is damaged, such as with corneal abrasion and retinal damage, or if a pupil(s) is unable to normally constrict (seen with damage to the oculomotor nerve).

Causes

Patients may develop photophobia as a result of several different medical conditions related to the eye or the nervous system.